Commercial paper products such as hand towels are manufactured from cellulosic base sheets. A cellulosic base sheet is a paper product in its raw form prior to undergoing conventional post-treatments such as calendaring and embossing. In general, cellulosic base sheets are made by preparing an aqueous suspension of papermaking fibers and injecting or depositing the suspension onto an endless sheet-forming fabric to form a wet-laid web, which is then dewatered and dried to produce a base sheet suitable for finish processing.
Because of its commercial availability and practicality, through-drying is often used to dry base sheets. Through-drying involves removing water from a wet-laid web by passing a heated gas (e.g., air) through the web. More specifically, through-air drying typically comprises transferring a partially dewatered, wet-laid web from a sheet-forming fabric to a coarse, highly permeable through-drying fabric. A stream of heated air is passed through the wet web carried on the through-drying fabric as it runs over the high permeability rotating cylinder or drum of a through-drying apparatus. As the hot, dry air contacts the wet web, water is evaporated from the web and is transferred to the flow of drying air. Processes for making cellulosic base sheets including through-drying are described, for example, in U.S. Pat. No. 5,607,551 (Farrington et al.) and U.S. Pat. No. 6,149,767 (Hermans et al.), the entire disclosures of which are incorporated herein by reference.
It has been observed that a strong, burnt popcorn-like odor is sometimes emitted from finished paper hand towels when the towels are wetted (i.e., re-wetted after final drying of the base sheet from which the towel is made). Upon investigation, this problem of malodor release has been found to be particularly present in paper products made from cellulosic base sheets that have been through-air dried at relatively high air temperatures. It was hypothesized that over-drying or over-heating of the base sheets was leading to the malodor problem upon re-wetting of the paper product. By operating the through-air drying stage of a base sheet manufacturing process at a lower air temperature and compensating with slightly longer sheet residence time on the drying drum, the malodor problem can be largely eliminated. However, longer residence times in the through-drying apparatus adversely affect the overall productivity of the base sheet manufacturing process.
Therefore, what is lacking and needed in the art is a process which can reduce or eliminate malodor released upon re-wetting of paper products, particularly those made from through-air dried cellulosic base sheets, while allowing higher air drying temperatures and shorter dryer residence times to be used to increase product throughput and productivity.